Deciduous fruit trees, grape vines and kiwifruit vines, shrubs, or bushes normally require enough winter chilling hours to produce a crop of fruit. The amount of chilling required depends upon the kind of fruit and the cultivar. Problems can arise in tropical and semi-tropical climates when there is no chilling, or in desert climate zones where there is insufficient chilling. The result of these problems can be growth abnormalities such as delayed and uneven blossoming, poor leaf cover, and insufficient or inconsistent fruit-set and reduced fruit size can occur. At the end of a vegetation period, such plants cease growing after bearing fruit and form buds. This budding enables a meristem, which has undifferentiated leaf and blossom structures, to survive under the unfavorable environmental conditions of winter because buds, in the latent stage, are much more resistant to frost and low temperatures than active tips of vegetation. Without sufficient chilling, the buds can be devoid of a commercially acceptable yield of fruit.
This latent stage is referred to as dormancy, and its duration is species specific and depends upon environmental conditions, such as the degree-day chilling factor. Dormancy is generally initiated by exposing buds to sufficient degree days' chilling. This means that the dormancy can generally only be terminated if the buds have been exposed to degree days' chilling that are insufficient to continue dormancy, followed by an experience of elevated temperatures.
In grape and fruit growing areas, mild winters with dormancy that are either not strong enough, not long enough, or that are non-existent, can cause delayed or reduced bud break or development. The result is an unreliable and inconsistent development of blossoms and fruit, which can produce markedly reduced crop yields. Moreover, dormancy either does not occur, does not occur to an appreciable extent, or needs to be forced in regions that do not have an ideal natural climate for grape and other deciduous fruit growing. For example, tropical or semi-tropical areas, such as regions of Peru and Brazil, do not have any chilling. As another example, desert regions, such as the Coachella Valley in California or Hermosillo, Mexico, have insufficient chilling, and therefore dormancy does not occur to an appreciable extent. Even in regions with temperate or Mediterranean climates, there is the possibility of irregularity of dormancy.
These problems are of greater practical significance in those climates in which the necessary cold stimulus is absent. These problems can also occur with the use of cultivars that are not adapted to local conditions that lack dormancy.
There has been an effort to control bud dormancy by artificial intervention. Successful attempts have been made to interrupt bud dormancy by using natural and synthetic growth substances. U.S. Pat. No. 4,487,625 described methods of treatment the dormant buds of grapevines by use of an aqueous cyanamide solution with a content of 0.1-10 weight percent as a means for interrupting bud dormancy. Hydrogen cyanamide, for example Dormex®, Hi-Cane™, and other chemical equivalence of hydrogen cyanamide, have been used to break dormancy on fruit crops worldwide to compensate for a lack of winter chilling and/or to initiate an earlier and more even fruiting bud break. It is thought that Hydrogen cyanamide acts as a plant growth regulator. For example, Dormex® has been used to produce table grapes in regions with tropical or semi-tropical climates, such as the Sáo Francisco valley in Brazil, where the vines and plants do not attain sufficient chilling hours to initiate dormancy at all. In addition, Dormex® has been used to produce table grapes in desert climates such as California's Coachella Valley and Hermosillo in Mexico, where insufficient chilling occurs. As another example of the use of a version or chemical equivalent of hydrogen cyanamide, Hi-Cane™ has been used in the temperate climate of New Zealand on kiwifruit vines to initiate an earlier and more even fruiting bud break. However, hydrogen cyanamide is a skin and eye irritant, and is especially acute when used in combination with the consumption of alcohol. Moreover, grape and other fruits grown with the use of hydrogen cyanamide cannot be certified as organically grown. Also, over time, the use of hydrogen cyanamide can lower the fruitability of vines by as much as 20-30% per year. Finally, the drift of hydrogen cyanamide sprays can potentially injure nearby citrus trees.
Therefore, there remains a need in the art for a method of inducing bud break or dormancy break without the use of plant growth regulators or harsh chemicals such as hydrogen cyanamide. Insufficient dormancy of chilling creates nutritional inconsistency in the plants. These nutritional deficiencies or excesses are addressed by the formula of the present invention. Whereas Dormex®, Hi-Cane™, and any other version or equivalent of hydrogen cyanamide, overcome these inconsistencies by regulating the growth of the plants, the formulas of the present invention are not plant growth regulators and address the inconsistencies purely nutritionally. As a result, the compositions of the present invention work to produce a high enough percentage of fruiting buds to get commercially acceptable crop yields and/or to initiate an earlier and more even fruiting bud break in tropical or semi-tropical climates, in desert climates, and in temperate or Mediterranean climates. Moreover, the fruit obtained by the methods of this invention are not prevented from being certified organic.